A study was conducted to determine how Hispanic bilingual students’ knowledge of Spanish vocabulary and ability to identify Spanish-English cognates relate to their comprehension of English expository text. Subjects, 74 upper elementary Hispanic students able to read in both Spanish and English, were tested for Spanish and English vocabulary knowledge, and after reading each of four expository texts containing English words with Spanish cognates (e.g., English transform and Spanish transformar) were given a multiple-choice test on their understanding of key concepts from these texts. After a brief explanation of the concept cognate, they were asked to identify the words in these texts that had Spanish cognates. Performance on the multiple-choice test was found to be related to students’ ability to recognize cognate relationships. The relationship between Spanish vocabulary knowledge and English reading comprehension also appeared to depend on students’ ability to recognize cognates.